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Chlorphenesin carbamate is a skeletal muscle relaxant, and one of its metabolites is 4-chlorophenoxyacetic acid (4-CPA), which is included on the Prohibited List of the World Anti-Doping Agency (WADA). The non-prohibited substance, chlorphenesin carbamate, as a potential source of 4-CPA, needs to be identified more strongly in doping control protocols. In this paper, the metabolism of chlorphenesin carbamate in human urine was studied. Ten volunteers were recruited to take chlorphenesin carbamate tablets orally, and urine samples were collected before and after being tested. The urine samples were detected by liquid chromatography-Q Exactive HF orbitrap mass spectrometry (LC-Q Exactive HF-MS) in full MS and full MS-ddMS 2 scanning modes. Based on accurate molecular formulae determination and fragmentation pattern analysis by mass spectrometry, a total of 29 chlorphenesin carbamate metabolites were found, comprising 18 newly identified metabolites and 11 previously reported metabolites. There were five potential metabolic processes listed: hydroxylation, amide hydrolysis, C-oxidation, O-glucuronidation, sulfation, and their combinations. Chlorphenesin carbamate and the 29 metabolites were compared for their detection windows, and the findings indicated that the two recently reported metabolites, M9 and M10, had longer detection windows than the metabolites documented by the WADA. These metabolites are anticipated to be long-lasting biomarkers for the detection of chlorphenesin carbamate intake. By analyzing the results of metabolomic profiling, it was found that the metabolites with significant changes were mainly related to histidine metabolism and β-alanine metabolism pathways. This paper provides a comprehensive report on the metabolic profile of urinary chlorphenesin carbamate and reveals a point of view the changes in the metabolic in the human body, which is conducive to supporting the detection of chlorphenesin carbamate and meclofenoxate for doping control, as well as a better understanding of the mechanism of action of chlorphenesin carbamate as a drug., (© 2024 John Wiley & Sons Ltd.)

Rationale: Chlorphenesin is an approved biocide frequently used in cosmetics, and its carbamate ester is an approved skeletal muscle relaxant in certain countries for the treatment of discomfort related to skeletal muscle trauma and inflammation. A major urinary metabolite is 4-chlorophenoxy acetic acid (4-CPA), also known as para-chlorophenoxyacetate, which is also employed as a target analyte in sports drug testing to detect the use of the prohibited nootropic stimulant meclofenoxate. To distinguish between 4-CPA resulting from chlorphenesin, chlorphenesin carbamate, and meclofenoxate, urinary metabolite profiles of chlorphenesin after legitimate use were investigated., Methods: Human administration studies with commercially available sunscreen containing 0.25% by weight of chlorphenesin were conducted. Six study participants dermally applied 8 g of sunscreen and collected urine samples before and up to 7 days after application. Another set of six study participants applied 8 g of sunscreen on three consecutive days, and urine samples were also taken for up to 5 days after the last dosing. Urine specimens were analyzed using liquid chromatography-high resolution (tandem) mass spectrometry, and urinary metabolites were identified in accordance with literature data by accurate mass analysis of respective precursor and characteristic product ions., Results: In accordance with literature data, chlorphenesin yielded the characteristic urinary metabolites, chlorphenesin glucuronide, chlorphenesin sulfate, and 3-(4-chlorophenoxy)-2-hydroxypropanoic acid (4-CPP), as well as the common metabolite 4-CPA. 4-CPA and 4-CPP were observed at similar abundances, with urinary concentrations of 4-CPA reaching up to ~1500 and 2300 ng/mL after single and multiple sunscreen applications, respectively., Conclusion: 4-CPA is a common metabolite of meclofenoxate, chlorphenesin, and chlorphenesin carbamate. Monitoring the diagnostic urinary metabolites of chlorphenesin provides conclusive supporting evidence of whether chlorphenesin or the prohibited nootropic meclofenoxate was administered., (© 2021 The Authors. Rapid Communications in Mass Spectrometry published by John Wiley & Sons Ltd.)

We synthesized galactosyl chlorphenesin (CPN-G) using β-gal-containing Escherichia coli (E. coli) cells in which the conversion yield of chlorphenesin (CPN) to CPN-G reached about 64 % during 12 h. CPN-G was identified and characterized using high-performance liquid chromatography, liquid chromatography-mass spectrometry, Fourier transform-infrared spectrometry, and nuclear magnetic resonance analysis ((1)H and (13)C). We verified that a galactose was covalently bound to a CPN alcohol group during CPN-G synthesis throughout these analyses. In particular, by the hydrolysis of CPN-G using β-gal, it was confirmed that a galactose was bound to CPN. The minimal inhibitory concentration (MIC) results showed that the CPN-G MICs were fairly similar to those of CPN. HACAT cell viability was significantly higher in CPN-G-treated cells than in CPN-treated cells at concentrations of 0.0-20.0 mM. Finally, we accomplished the synthesis of less toxic CPN-G, compared with CPN, using β-gal-containing E. coli cells as whole cells without changes in the MICs against microorganisms.

A facile, high regioselective enzymatic synthesis approach for the preparation of amphipathic prodrugs with saccharides of mephenesin and chlorphenesin was developed. Firstly, transesterification of two drugs with divinyl dicarboxylates with different carbon chain length was performed under the catalysis of Candida antarctica lipase acrylic resin and Lipozyme in anhydrous acetone at 50 degrees C, respectively. A series of lipophilic derivatives with vinyl groups of mephenesin and chlorphenesin were prepared. The influences of different organic solvents, enzyme sources, reaction time, and the acylation reagents on the synthesis of vinyl esters were investigated. And then, protease-catalyzed high regioselective acylation of D-glucose and D-mannose with vinyl esters of mephenesin and chlorphenesin gave drug-saccharide derivatives in good yields. The studies of lipophilicity and hydrolysis in vitro of prodrugs verified that drug-saccharide derivatives had amphipathic properties, and both lipophilic and amphipathic drug derivatives had obvious controlled release characteristics.

A new approach to galacto-oligosaccharides and galacto-conjugates synthesis performed by the beta-galactosidase from Kluyveromyces lactis is reported. The enzymatic galactosylation of eight kinds of adsorbed aromatic primary alcohols, in particular the two drugs guaifenesin and chlorphenesin, gave the corresponding beta-D-galacto-pyranosides in yields ranging between approximately 10% and 96%. For the first time, we have showed that the adsorption of acceptor substrates onto solid supports such as silica gel influences the yield and the selectivity of galacto-conjugates synthesis. In particular, we observed that adsorption of acceptor favored the synthesis of digalactosylated compounds.